var print = console.log
var a = new Number(5)
console.log(Number(a))
console.log(a<Number.MAX_VALUE)
print(a>Number.MIN_VALUE)
print(Number.NEGATIVE_INFINITY)
print(a>Number.POSITIVE_INFINITY)
print(a.toString(16))    //转换成字符串  参数可以写进制基数
print(a.toFixed(2))  //转换成a后边加小数点
console.log(a.toExponential()) //转换成指数形式的字符串 一般用不上
print(a.toPrecision(3))  //转换成小数点形式的字符串
print(typeof(a))
print(typeof(a.valueOf()))    //返回number类型
print(Number.NEGATIVE_INFINITY)
print(Number.POSITIVE_INFINITY)
print(typeof NaN)


var undefined = "abc"
print(undefined)
print("undefined输出" + typeof undefined)